Ejector type punch

ABSTRACT

A PIERCING OR FORMING PUNCH ASSEMBLY HAVING A HEADED RECIPROCABLE EJECTOR MEMBER ACCOMMODATED IN THE PUNCH BODY. A UNIQUELY FORMED URETHANE WASHER OR LIKE DEVICE IS FITTED AROUND THE SHANK OF THE EJECTOR MEMBER TO THE UNDERSIDE OF THE HEAD THEREOF TO ACT AS A LOAD DISTRIBUTING   AND SHOCK ABSORBING MEDIUM. THE WASHER IS CONSTRUCTED TO PROVIDE A PUMP SUPPLYING AIR TO THE WORKING FACE OF THE PUNCH FOR VACUUM BREAKING AND DEBRIS CLEARING PURPOSES.

NOV- 16, 197l R. J. GARGRAVE EJECTOR TYPE PUNCH Filed Sept. 8, 1969 VVE/V701? ROBERT J. GARGRAVE BVM Vf/Sffow FIG-6 ATTORNEY 3,620,113 Patented Nov. 16, 1971 hee 3,620,113 Y EJECTOR TYPE PUNCH Robert J. Gargrave, Dayton, Ohio, assignor to Dayton Progress Corporation, Dayton, Ohio Filed Sept. 8, 1969, Ser. No. 856,125 Int. Cl. B26f 1/14 U.S. Cl. 83-98 1S Claims ABSTRACT OF THE DISCLOSURE A piercing or forming punch assembly having a headed reciprocable ejector member accommodated in the punch body. A uniquely formed urethane washer or like device is fitted around the shank of the ejector member to the underside of the head thereof to act as a load distributing and shock absorbing medium. The washer is constructed to provide a pump supplying air to the working face f the punch for vacuum breaking and debris clearing purposes.

BACKGROUND OF THE INVENTION This invention relates to improvements in forming and piercing type punches. It has especial although not limited reference to ejector type punches and, for purposes of illustration, will be particularly described in its broad application to piercing type punch units and assemblies.

In its specific illustrated form the invention provides an embodiment representing an improvement upon the punch of Robert A. Gargrave shown in his United States Letters Patent No. 2,917,960 dated Dec. 22, 1959. The patented punch is an ejector type punch including a punch body having a working face and a longitudinal bore opening through such face. An ejector pin is accommodated in the bore and has a headed inner end which seats in a counterbore within the punch body. A spring in the counterbore is based on a set screw applied therein to produce an axially directed thrust to the ejector pin, seating the head end of the pin to a shoulder formed in the bottom of the counterbore. This causes the outermost end of the ejector pin to normally be projected relative to the working face of the punch body. The punch body is applied to a work piece in a manner to cut a blank or slug therefrom and in the process the ejector pin is deflected inwardly of the body, compressing the biasing spring. As the slug or blank is cut from the work piece, the ejector pin is released to be again projected outwardly by the spring and in the process to dislodge the cut blank from the working face of the punch. According to a further feature of the patented device, the punch body has an opening in the wall thereof through which stop means may be inserted to underlie the head end of the ejector pin whereby to achieve a retracted position thereof. This arrangement permits grinding of the working face of the punch body and the outer end of the ejector pin in unison so that sharpening of the punch will not alter the relationship required between the punch body and the ejector pin.

The Gargrave punch above described has substantially advanced the art of piercing punches and continues in successful Widespread use. Such use has, however, revealed problem areas as related to certain high impact applications. In some instances the shock of impact of the head of the ejector pin on the bottom of the counterbore has been such to create a fracture and breakage of the ejector pin. In other instances it has been determined that vacuum forces of an undesirable level are created at the punch face, causing a cut blank to adhere to the punch body to a degree to interfere with a smooth procedure in an automated punching operation. In some instances the materials and the environment has been such that there has been a tendency in the punching operation for debris and cut particles to collect and build up around the ejector pin at the entrance of its accommodating bore. This tends to restrict the free movement and proper function of the ejector pin.

SUMMARY OF THE INVENTION The instant invention is directed to a solution of the above mentioned problems in certain areas of application of ejector type punches. The improved punch assembly here provided features the use of a lighter Weight and more economical ejector pin to which is applied a pumping element in the form of a resilient, deformable pad or washer of urethane or like material. The latter is mounted on the pin to form a pumping cushion interposed between the pin head and its normal seat in the counterbore of the punch per se. The effect is to substantially reduce impact shocks and the possibility of the breakage or fracture of the pin head. The pad is designed to have a press fit or is otherwise applied about the pin shank immediately beneath the head. In effect, it becomes part of the head on the pin and, in accordance with the invention, permits the use of a smaller integrally formed pin head and a pin body which may be reduced to a wire-like form. As a part of the head means, the pad moves with the pin and can serve as a medium by which the pin may be held in a retracted position for grinding of the working face of the punch.

In the preferred embodiment illustrated, the peripheral configuration of the Vpad is such to provide it with a circumferentially projected pumping ap or skirt which is biased into contact with the internal wall of the counterbore of the related punch body. The configuration of the pad is such to allow some eccentricity of movement of the pad center line with respect to the center line of the punch without loss of contact with the punch body. It also provides that the outwardly thrusting and retracting movements of the ejector pin, occurring in use of the punch, may be utilized to pump air through the longitudinal bore in which the pin shank is accommodated. This action helps break the vacuum Which may occur between the punch face and a cut blank or the like and tends to keep the bore of the punch clear of dirt, chips and flakes which would otherwise diminish the effectiveness of the operation of the ejector pin.

This described pumping action, together with the cushioning effect achieved by the inserted pad or washer, make possible a simplified and more cheaply fabricated ejector pin, for example one formed of wire. Such is much more cheaply and simply fabricated than a machined ejector pin such as heretofore required. In a further improvement of the invention, the set screw which in the prior art provides a base for a confined compressiontype ejector spring for backing the ejector pin is eliminated. Instead, the invention contemplates the use in the punch counterbore of a backing spring having selffxing characteristics. Such facilitates the assembly and maintenance of the. punch devices of the invention.

A primary object of the invention is to provide an improved ejector type punch which is more efficient and satisfactory in use, more versatile in application and unlikely to malfunction.

Another object of the invention is to provide a more economical and more effective ejector type punch.

A further object of the invention is to provide an ejector type punch which introduces a concept of cushioning whereby a reciprocable headed ejector member is supported in a punch by a pump element in the form of a urethane washer or the like for shock absorbing and allied purposes.

A further object of the invention is to utilize shock absorbing means in an ejector type punch as a means to dispel vacuum and producing a self-cleaning of the punch assembly.

Still another object of the invention is to provide an ejector type punch especially adapted to enable a simplified, inexpensive production and maintenance thereof.

An additional object of the invention is to provide an improved ejector type punch possessing the advantageous structural features, the inherent meritorious characteristics and the means and mode of use herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawings wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

FIG. 1 is a longitudinal section of an ejector punch in accordance with a preferred embodiment of the invention;

FIG. 2 is a cross-sectional view taken substantially along the line 2-2 of FIG. 1;

FIG. 3 is a side elevation of the multi-purpose pumping pad comprised in the invention pump illustrated;

FIG. 4 is a `view showing the underside of the pad of FIG. 3;

FIG. 5 is a partly diagrammatic view showing a piercing punch as in FIG. l in an operational environment; and

FIG. 6 is a detail, fragmentary View, showing parts of the punch in a position they assume after cutting of a blank from a work piece.

Like parts are indicated by similar characters of reference throughout the several views.

IReferring to the drawings, a piercing punch in accordance with the illustrated embodiment of the invention comprises a punch body 10 conventionally including an intermediate barrel portion 11 of uniform diameter terminating at one end in an expanded external flange portion 12 and at its opposite end in a reduced diameter punch portion 14. The transition surface 13 at the outer periphery of the punch which interconnects the barrel portion 11 and punch portion 14 has an arcuate form.

The punch portion 14 terminates in a sharp edged work engaging face 15 which lies in a plane perpendicular to the longitudinal axis of the punch body. Of course, it will be obvious that the cross-sectional shape of the punch portion 14 will be so designed to meet the requirements of its particular application.

The body 10 has a longitudinal through bore 16 the longitudinal axis of which coincides with that of the punch. This bore opens at one end from` the work engaging face 15 and is expanded at its opposite end by a counterbore 17 forming inwardly thereof a right angled shoulder 18 perpendicular to the bore axis. The shoulder 18 coincides with the junction of the barrel portion l1 and the immediately adjacent transition portion 13. A chamfer 20 is formed on the inner edge of the shoulder 18 providing a convergent conical surface extending in the direction of the working face 15. Note that there is formed in the sidewall of the barrel portion 11, immediately in advance of the shoulder 18, three circumferentially spaced apart and radially directed openings 19. The openings 19 are equidistant from one another and so provided as to permit the insertion therethrough of a limiting stop means as will hereinafter more clearly appear.

Mounted for freely reciprocable movement in the bore 16 is an ejector pin 21 which in accordance with a feature of the invention may be inexpensively fabricated from wire stock, for example. The pin 21 has a length to exceed the distance between the face 15 and the shoulder 18. The one end of the pin which projects into the counterbore 17 is formed to provide thereon a laterally expanded head 22. A coiled compression spring 23 is disposed in the counterbore 17 to bear at one end against the head 22 whereby to normally urge the pin 21 to project its opposite or remote end through and beyond the plane of the face 15. The spring 23 is of a screwless type in that it requires no set screw or other back-up device to be inserted in the outer end of the counterbore 17 to provide a limiting ibase therefor. With respect to its manner of introduction in the counterbore, the spring has a leading end portion 24 and a trailing end portion 25. End portion 24 engages the head 22 and may be considered its working end. Note that the respective end portions of the spring are differentially sized. Segment 24 has a smaller diameter than the segment 25. Moreover, the head abutting coils of segment 24 are wound in such spaced relation as to enable relatively free compression and extension thereof in applying continuous axial thrust to the head 22. In contrast, spring segment 25 has a larger diameter and a more compacted form, the coils thereof being closely wound. The diameter of the coil segment 24 is such to be freely received within the counterbore 17 while the diameter of segment 25, on the other hand, is made to somewhat exceed the diameter of the counterbore 17. This enables the trailing end of the spring to be utilized as a self-locking or anchoring means to insure that on contraction and insertion it will be retained in the counterbore and under conditions wherein the head 22 is properly and continuously loaded to serve its intended function.

lMounted about the pin and interposed between the head 22 and the shoulder 18 is a resilient deformable axially extended pad or washer 26. In the illustrated instance the washer is made of a urethane or like material. Pad 26 is annular in cross-section and has a central through opening of a size to permit the pad to be slipped over the pin 21 and positioned thereabout beneath head 22 with a press t. The backing pad effectively extends the length and diameter of the pin head so the latter may be made relatively small. The ends of the pad are at to seat squarely to both the shoulder 18 and the underside of head 22. At the outer periphery thereof the pad 26 has a portion 28 having a generally conical skirt-like configuration, the pad being so oriented that the broader or base end seats to the shoulder 18. At its opposite or apex end the pad has a diameter less than the internal diameter of counterbore 17. Attention is directed to the fact that the base end of the pad has a diameter to place the projected skirt extremity under compression in peripheral contact with the wall of the counterbore 17. Also, at the base end thereof the body and skirt of the pad define therebetween an annular groove 27, the skirt forming a surrounding flexible flap 28 thereabout.

As designed, the flap 28 is capable of free flexing and normally biased towards the punch axis as it remains in continuous contact with the wall of counterbore 17. It thus contacts the counterbore wall so that there is a resilient pressure thereon, the bias of the ap being such that there is a continuous contact, even where a slight eccentricity occurs in the position of the pad or the movement of its center line with respect to the center line of the punch body during the operation of the punch. Thus formed, the pad will act as a pumping element, the skirt portion thereof responding to an upward reciprocating movement of the pin 21 to pass air under pressure thereby and responding to the downward movement of the pin 21 to cup and force air thereunder past the chamfer 20 and into the bore 16. It is noted that there are formed on the underside of the pad 26, or that end thereof seating to shoulder 18, radially directed slots or recesses 29 for maintaining continuing communication between the bore 16 and the annular groove 27 in the bottom of the pad 26.

The benefits in operational use of the punch assembly above described may be more particularly evident from reference to FIGS. and 6 of the drawing. There shown is a piercing punch assembly of a kind to which the in- Stant invention punch may be applied. Schematically illustrated is a back-up plate 31 having Xed thereunder and co-extensively therewith a punch retainer plate 32. In a vertically aligned spaced apart re'lation therebelow is a lower die plate 33 apertured to receive therein an annular insert die 34 backed on its underside by a lower die shoe 35. Intermediately disposed is a stripper plate 36. The retainer 32 is provided with a through bore 37 having a counterbore 38 opening from the face thereof abutting the back-up plate 31. The punch body previously described is inserted to have its barrel portion 11 closely accommodated by the bore 37 while the flange end 12 seats in abutted relation to the back-up plate and against the shoulder formed by the counterbore 38. The barrel portion of the punch projects through and beyond its retainer to have the openings 19 in the body wall clear thereof. Punch portion 14 is axially projected in an aligned relation to an opening 39 in the stripper plate 36 and the opening defined by the annular die insert 34. Accord- `ing to the operation of assemblies of this kind, a work piece such as a sheet of metal material 41 may be fed across the upper surface of the die plate 33 and as this occurs the separate assemblies 31-32 and 33-35 caused to reciprocate relatively to one another. In response to an approaching motion, the punch face 15 passes through the opening 39 in the stripper p'late to engage and perforate, for example, the sheet 41, the continued approaching motion of the assemblies as described resulting in a blank portion of the sheet being cut therefrom. This blank is in line with the opening in the die insert 34 and of smaller dimension than such opening. Accordingly, the blank B (FIG. 6), thus created, is driven into the die insert 34 to eventually pass therefrom throu-gh an opening 42 in the die shoe 35 thereunder. In cutting the blank, the punch portion thus passes through the sheet 41 and it is normally contemplated that on the retracting stroke of the punch the stripper member 36 will be effective to restrain the sheet 41 from following the punch.

The ejector pin 21 is provided to serve in the direction of dislodging the cut blank from the work engaging surface 15. Many times, however, instead of dropping freely from the punch assembly, a cut blank B, as the punch retracts, tends to adhere to the work face 15. It will be apparent that since the compression spring 23 is relatively light and will yield when the projecting part of the ejector pin originally contacts the sheet 41, on contact the pin will be driven inwardly of the punch body. As the blank is cut, the load on the spring 23 is relieved, whereupon there is a reactant pressure, the energy of the spring 23 previously stored being released to apply a thrust to drive the ejector pin 21 outwardly of the punch body. Where there has been a lubricant used or materials worked on of a particular character, there is a vacuum produced which substantially increases the clinging tendencies of the cut blank. This is where the present invention comes into play.

In the action of the punch assembly the pad or -washer 26 effectively cushions even high degrees of impact shock which would normally occur in the pin head on returning to its seat on the shoulder 18. Moreover, the form and nature of the washer or pad 26 is such that it tends to evenly dissipate the involved forces applied to the head `and body portion of the ejector pin. This tends to fully minimize any tendency of a resultant fracture or breakage of the pin head from the pin body.

Further, in the course of the inwardly deieeting movement of the pin 21, as it contacts and reacts to the contact with the sheet 41, the ap or skirt 28 which is backed by air contained in the counterbore thereabove deects to permit the passage thereby of a portion of such air. Then, on the reactant stroke of the ejector pin, as it tends to be thrust outwardly by the spring 23, there is air trapped beneath the pad 26 and in the groove 27 thereof which is forced by the pad past the chamfer 20 and into the bore 16 and outwardly of the bore around the shank of the pin 21 to discharge at the face 15. The effect is a jet-like flow of air about the pin which has a pressure impact or influence on any cut blank which'tends to adhere closely to the punch working surface 15. The vacuum is broken thereby and the cut blank will be, almost instantaneously with the removal of the impact load on the ejector pin, discharged through the annular die insert in the lower die plate and the aperture 42 in the shoe thereunder. It will be apparent that in addition to insuring an immediate separation of a cut blank from the working face of a punch, the air flowing down around the pin 21 and from the working face will cleanse the bore and the face of any dust or cut particles Which would otherwise tend to collect there and eventually restrict the free movement and operation of the ejector pin.

It must be understood that the pumping aspect of the improved ejector pin assembly adds thereto a factor of efficiency for diicult applications which insures that under such conditions that a punching operation will be clean, quick and eflicient and avoid any possibility of malfunction or interference with timing, particularly in automated punching operations. Note that a factor of safety is provided in the preferred embodiment illustrated by provision for the radial slots or grooves 29 in the bottom of thepumping element 26 in co-operative and communicative relation with the bore 16 by way of the chamfered portion 20 and with the groove 27 in which air may be trapped in the downward or projecting movement of the ejector pin assembly.

As far as the radial openings 19 are here provided in spaced relation about the barrel portion of the punch, immediately adjacent the shoulder 18, this facilitates that upon a pushing inwardly of the ejector pin a keeper 43 may be inserted under the element 26 from an accessible position. As in previous punch elements, the purpose of this is to enable a periodic grinding of the work face 15 to maintain it in a good operating condition.

It has been found that the nature and the shock absorbing and dissipating characteristics of the pad 26 is such so one may elfectively utilize an ejector pin or wire the head of which is formed to be slightly larger than the body to serve as an abutting surface for the pad 26 which in effect provides an integral part and extension thereof which has pumping characteristics. Of course, where such may be desired, the pad 26 may be adhesively bonded to a wirelike ejector pin in the position illustrated. The economies introduced into the ejector type punch fabrication should be readily evident. v

In respect to the pumping efficiency of the pad 26, the simplicity Kof its construction in the preferred embodiment and the nature of its construction is such as to very simply and effectively insure tnat with any reciprocating movement of the ejector pin 21 there is an air pumping function which may serve, if not required for dislodging a cut blank, at least for cleansing the punch bore about the ejector pin and therefore prolonging its useful operative life. This last will not only permit a better function of the ejector pin under all conditions but will keep the working face clean and minimize any tendency of a work piece to adhere thereto or to the ejector punch in the form of a cut blank. Since in practically no case will the cut blank completely seal the bore, the eliiciency of the pumping action here described is optimal and its function is such to indeed afford an advance in the art.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of adavntage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of part without departingy from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specic features shown, but that the means and construction herein disclosed comprise but one of several moves of putting the invention into effect.

Having thus described my invention I claim:

1. In a piercing punch including a punch body having a longitudinal through bore accommodating therein an ejector pin and means for biasing said pin to project outwardly of said bore at the working face of said punch; means in connection with said pin to move therewith in the operation of said punch, including means having a form to cushion and dissipate in diverse senses stress and impact forces applied to said ejector pin, and said means in connection with said pin including pumping means operating in a reciprocating movement of said pin to direct liuid under pressure through the bore of said punch and outwardly thereof through its working face whereby to clear said bore of foreign particles.

2. In a piercing punch including -a punch body having a longitudinal through bore accommodating therein an ejector pin and means for biasing said pin to project outwardly of said bore at the working face of said punch; means in connection with said pin to move therewith in the operation of said punch, including means having a form to cushion and dissipate in diverse senses stress and impact forces applied to said ejector pin, said ejector pin having a wire-like form and said means in connection therewith forming a head portion thereof, said punch body having a counterbore in which said head portion reciprocates in bearing relation to the wall thereof, and said head portion being resilient and being retained under compression within said counterbore.

3. In a piercing punch including a punch body having a longitudinal through bore accommodating therein an ejector pin and means for biasing said pin to project outwardly of said bore at the working face of said punch; means in connection with said pin to move therewith in the operation of said punch, including means having a form to cushion and dissipate in diverse senses stress and impact forces applied to said ejector pin, aid punch body having a counterbore in one end thereof accommodating a biasing spring in backing relation to the innermost end of said ejector pin which has in conenction therewith valve means to receive and pressure flow lluid from said counterbore and about said ejector pin to discharge from the working face of said punch.

4. A punch assembly as in claim 3 characterized by said valve means being an annular element of resilient compressible material including in the end thereof facing the base of said counterbore a peripheral skirt forming a pocket for receipt therein of air or other fluid which may be pressure flowed through said bore and about said ejector pin to the working face of said punch.

5. In a piercing punch including a punch body having a longitudinal through bore accommodating therein an ejector pin and means for biasing said pin to project outwardly of said bore at the working face of said punch;

8 means in connection with said pin to move therewith in the operation of said punch, including means having a form to cushion and dissipate in diverse senses stress and impact forces applied to said ejector pin, the bore of said punch being enlarged in cross section at the end thereof remote from said working face to define inwardly of said punch and spaced from said working face a shoulder, said ejector pin having an expansion at the inner end thereof which positions within said expanded portion of said bore and mounting thereabout a cushioning means in underlying relation to said expansion which is xed for movement with said pin to and from an abutting stress dissipating relation to said shoulder and the body of said punch, said cushioning means being a valving element.

6. A punch assembly as in claim 5 characterized by said ejector pin being a Wire element the expanded end of which forms a head of lesser dimension than the surrounding wall of the body of said punch, said cushioning means having the form of an annular element of resilient material the lateral dimensions of which are greater than said head and peripheral portions of which are in biased relation to said punch body.

7. Apparatus as set forth in claim 6 characterized by said cushioning means including an annular body having a peripheral divergent skirt forming in the cushioning means opposite said shoulder at least one pocket, said skirt being adapted to flex and to receive thereby a pressured flow of air and to cup said air in said pocket for driving the same through the bore of said punch t0 clear the passage provided thereby for said ejector pin.

8. Apparatus as set forth in claim 7 characterized by the base of said cushioning means opposite said shoulder having therein radially directed slots for communicating said pocket with said bore.

9. For use in a punch assembly having a longitudinal through bore opening at one end to the working face of the punch and at the other end to a counterbore, an ejector pin having in xed relation to the inner end thereof a valving element including in the base thereof means defining at least one pocket and adapted to receive in said pocket air which in the reciprocation of said pin will pump the same through said bore.

10. Apparatus as set forth in claim 9 characterized by means for maintaining communication between said bore and said pocket in the course of the pumping action aforementioned.

11. In a piercing punch including a punch body having a longitudinal through bore and at one end thereof a counterbore, the junction of said bore and counterbore defining a transverse shoulder, an ejector pin reciprocable in said bore in extending and retracting strokes and having `a head on an inner end portion accommodated in said counterbore, resilient reactant means disposing in said counterbore and arranged to be compressed by a retractig motion of said pin, said shoulder being positioned to limit extending motion of said pin under the urging of said reactant means, and means including cushoning material surrounding said ejector pin between said head and said shoulder.

12. A piercing punch according to claim 11 wherein said ejector pin and said head thereon are formed integrally of one another of wire stock or the like.

13. A piercing punch or the like `according to claim 11, wherein said last named means is formed of a resilient deformable material having a press fit about the ejector pin beneath the head to move with the head and being laterally expanded relatively to the head to achieve over at least a part of its length a contacting relation to the wall of the counterbore.

14. A piercing punch according to claim 13, wherein said last named means is made of a urethane plastic or like material.

1S. A piercing punch according to claim 11, wherein said longitudinal through bore is oversize relative to sa1d ejector pin to provide an air liow passage around the pin in said bore, said passage opening into said counterbore through said transverse shoulder,4 and said last named means having an end facing said head reduced in diameter relative to said counterbore and having an opposite end facing said shoulder constructed to form a flexible ap in compressive contact with the wall of the counterbore and peripherally reducing in diameter from said flap to the first said end thereof to be adapted thereby to perform the dual function of a cushion protecting said head and of a pump forcing air through said flow passage in said bore for vacuum breaking and debris clearing purposes.

References Cited UNITED STATES PATENTS 2,917,960 12/1959 Gargrave 83-140 3,063,319 11/1962 Johnson 83-698 X 3,233,487 2/1966 King 83-140 3,234,834 2/1966 Maurer 83-140 X JAMES M. MEISTER, Primary Examiner U.S. Cl. XR. 

